Is it permissible to combine Dhuhr and Asr prayers at one time, and Maghrib and Isha’ prayers at one time in a congregational prayer because of Coronavirus pandemic? If yes, can you supply us with the evidence?

Answer

Praise Be to Allah and Peace Be Upon His Messenger.
Referring to your question, combining each two prayers is permissible under restrictions. Because of illness, a Muslim can combine each two prayers; this is agreed upon by some Muslim scholars. However, combining prayers as a prevention from an infection is not permissible. Allah says: “The prayer is enjoined on the believers at fixed hours.” An-Nisa’: 103. 
A Muslim who is infected with the virus; and thus, he is sick, is allowed not to go to the mosque to perform the prayers in a congregation so as not to be a cause for infecting others. Moreover, if a Muslim fears being infected, they are allowed not to perform the prayer in the mosque. 
It is mentioned in the Prayer Jurisprudence Book which was issued by the Palestinian House for Fatwas that a sick who finds it hard to perform each prayer at its time can combine each two prayers. The evidence is what was narrated by Ibn Abbas: “The messenger of Allah (PBUH) prayed Dhuhr and Asr together, and Maghrib and Isha’ together, and not out of fear nor because of travelling.” Related by Muslim. Then, Ibn Abbas was asked by Waki’, “why did the prophet intend to do that. Ibn Abbas answered that the prophet did not want to put his Ummah to unnecessary hardship.
Thus, Ibn Hijr explained that such a combination which was narrated by Ibn Abbas was not done according to any reason such as fear, rain, or travel; that is why some scholars think it is permissible for the sick to combine each two prayers. (Fath Al-Bari: 2/35)
Imam Nawawi said that some scholars think what was done by the prophet was to permit Muslims who are sick to combine prayers because sickness is harder than rain. 
Finally, as combining prayers increases gathering which leads to increasing the opportunity of infection, it is not allowed.